Method and Apparatus for Calculating Distance in Contents Delivery Network

1. A method for calculating, by a name server, a distance between a local DNS (LDNS) and a point of presence (POP) in a content delivery network (CDN) including a client, the LDNS, the name server, the POP, and a probe server included in the POP, the method comprising: responsive to the name server receiving a domain name resolution request from the LDNS, generating, by the name server, a canonically named (CNAME) domain name reply by adding an identifier to a resolution-requested domain name corresponding to the domain name resolution request; and transmitting, by the name server, the CNAME domain name reply to the probe server, wherein a source IP address corresponding to the CNAME domain name reply transmitted to the probe server is changed to the address of the name server by the probe server and delivered to the LDNS, wherein the name server receives a resolution request for the CNAME domain name reply from the LDNS, wherein the name server calculates a time based distance between the LDNS and the POP by subtracting a time based distance between the name server and the LDNS and a time based distance between the name server and the probe server from a total time from when the CNAME domain name reply is transmitted from the name server to the probe server to when the name server receives the resolution request for the CNAME domain name reply from the LDNS.

2. A method for calculating, by a name server, a distance between a local DNS (LDNS) and a point of presence (POP) in a content delivery network (CDN) including a client, the LDNS, the name server, the POP, and a probe server included in the POP, the method comprising: responsive to the name server receiving a domain name resolution request from the LDNS, generating, by the name server, a CNAME domain name reply by adding an identifier to a resolution-requested domain name corresponding to the domain name resolution request; and transmitting, by the name server, the CNAME domain name reply to the probe server, wherein a source IP address corresponding to the CNAME domain name reply transmitted to the probe server is changed to the address of the name server by the probe server and delivered to the LDNS, wherein the name server receives a resolution request for the CNAME domain name reply from the LDNS, wherein the name server receives information about a time when the CNAME domain name reply is transmitted from the probe server to the LDNS and the name server calculates a time based distance between the LDNS and the POP by subtracting a time based distance between the name server and the LDNS from a total time that is based on the time when the CNAME domain name reply is transmitted from the probe server to the LDNS and a time when the name server receives the resolution request for the CNAME domain name reply from the LDNS.

3. A method for calculating, by a probe server, a distance between a local DNS (LDNS) and a point of presence (POP) in a content delivery network (CDN) including a client, the LDNS, a name server, the POP, and the probe server included in the POP, the method comprising: receiving by the probe server, a CNAME domain name reply from the name server, the CNAME domain reply generated by receiving a domain name resolution request from the LDNS and adding an identifier to a resolution-requested domain name corresponding to the domain name resolution request; changing, by the probe server, a source IP address corresponding to the received CNAME domain name reply to the address of the name server and transmitting the address of the name server to the LDNS; receiving, by the probe server, information about a time when the name server receives a resolution request for the CNAME domain name reply from the LDNS and information about a time based distance between the name server and the LDNS from the name server; and calculating, by the probe server, a time based distance between the LDNS and the POP by subtracting the time based distance between the name server and the LDNS from a total time that is based on the time when the CNAME domain name reply is transmitted to the LDNS and a time when the resolution request for the CNAME domain name reply from the LDNS is received from the name server.

4. The method according to one of claims 1 , 2 and 3 , wherein the probe server is installed in the POP in the form of a program.

5. The method according to one of claims 1 , 2 and 3 , wherein the time based distance between the name server and the LDNS is calculated through at least one of a ping test and trace route.

6. The method according to one of claims 1 , 2 and 3 , wherein the time based distance between the name server and the LDNS is calculated using a time for which the name server generates the CNAME domain name reply for the resolution-requested domain name upon receiving the domain name resolution request from the LDNS, transmits the CNAME domain name reply to the LDNS and receives the CNAME resolution request from the LDNS.

7. The method according to one of claims 2 and 3 , wherein the name server and the probe server are synchronized with each other.

8. The method according to one of claims 1 , 2 and 3 , wherein the calculating of the time based distance between the LDNS and the POP is applied only when the probe server cannot directly calculate the time based distance between the LDNS and the POP.

9. The method according to claim 8 , wherein the probe server directly calculates the time based distance between the LDNS and the POP using at least one of the ping test and trace route.

10. A name server for calculating a distance between a local DNS (LDNS) and a point of presence (POPS) in a content delivery network (CDN) including a client, the LDNS, a name server, the POP, and a probe server included in the POP, the name server comprising: a domain name resolution unit for transmitting, to the LDNS, an IP address matched to a domain name corresponding to a domain name resolution request responsive to the domain name resolution request being received from the LDNS; a CNAME generation unit for generating a CNAME domain name reply by adding an identifier to the resolution-requested domain name; a network state detection unit for calculating a time based distance between the LDNS and the name server; a distance calculation unit for calculating a time based distance between the LDNS and the POP; and a communication unit for receiving the domain name resolution request from the LDNS, transmitting the CNAME domain name reply to the probe server and receiving a domain name resolution request from the LDNS, wherein a source IP address corresponding to the CNAME domain name reply transmitted to the probe server through the communication unit is changed to the address of the name server by the probe server and delivered to the LDNS, wherein a resolution request for the CNAME domain name reply is received from the LDNS through the communication unit, wherein the distance calculation unit calculates the time based distance between the LDNS and the POP by subtracting a time based distance between the name server and the LDNS and a time based distance between the name server and the probe server from a total time from when the CNAME domain name reply is transmitted from the name server to the probe server to when the name server receives the resolution request for the CNAME domain name reply from the LDNS.

11. A name server for calculating a distance between a local DNS LDNS and a point of presence (POPS) in a content delivery network (CDN) including a client, the LDNS, a name server, the POP, and a probe server included in the POP, the name server comprising: a domain name resolution unit for transmitting, to the LDNS, an IP address matched to a domain name corresponding to a domain name resolution request responsive to the domain name resolution request being received from the LDNS; a CNAME generation unit for generating a CNAME domain name reply by adding an identifier to the resolution-requested domain name; a network state detection unit for calculating a time based distance between the LDNS and the name server; a distance calculation unit for calculating a time based distance between the LDNS and the POP; and a communication unit for receiving the domain name resolution request from the LDNS, transmitting the CNAME domain name reply to the probe server and receiving a domain name resolution request from the LDNS, wherein a source IP address corresponding to the CNAME domain name reply transmitted to the probe server through the communication unit is changed to the address of the name server by the probe server and delivered to the LDNS, wherein a resolution request for the CNAME domain name reply is received from the LDNS through the communication unit, and information about a time when the CNAME domain name reply is transmitted from the probe server to the LDNS is received, wherein the distance calculation unit calculates the time based distance between the LDNS and the POP by subtracting a time distance between the name server and the LDNS from a total time that is based on the time when the CNAME domain name reply is transmitted from the probe server to the LDNS and a time when the name server receives the resolution request for the CNAME domain name reply from the LDNS.

12. A probe server for calculating a distance between a local DNS (LDNS) and a point of presence (POP) in a content delivery network (CDN) including a client, the LDNS, a name server, the POP, and the probe server included in the POP, the probe server comprising: a network state detection unit for calculating a time based distance between the probe server and the name server; a source IP address change unit for changing a source IP address to the IP address of the name server when a CNAME domain name reply received from the name server is delivered to the LDNS, wherein the CNAME domain name reply received from the name server is generated by the name server by receiving a domain name resolution request from the LDNS and adding an identifier to a resolution-requested domain name corresponding to the domain name resolution request; a distance calculation unit for calculating a time based distance between the LDNS and the POP; and a communication unit for receiving a resolution request for the CNAME domain name reply from the name server, transmitting, to the LDNS, the CNAME domain name reply, for which the source IP address is changed by the source IP address change unit, and receiving, from the name server, information about a time when the resolution request for the CNAME domain name reply is received from the LDNS and information about a time based distance between the name server and the LDNS, wherein the distance calculation unit calculates the time based distance between the LDNS and the POP by subtracting the time based distance between the name server and the LDNS from a total time that is based on the time when the CNAME domain name reply is transmitted to the LDNS and a time when the resolution request for the CNAME domain name reply from the LDNS is received from the name server.

13. The apparatus according to one of claims 10 , 11 and 12 , wherein the probe server is installed in the POP in the form of a program.

14. The apparatus according to one of claims 10 , 11 and 12 , wherein the network state detection unit calculates the time based distance between the name server and the LDNS through at least one of a ping test and trace route.

15. The apparatus according to one of claims 10 and 11 , wherein the network state detection unit calculates the time based distance between the name server and the LDNS using a time for which the name server generates the CNAME domain name reply for the resolution-requested domain name when receiving the domain name resolution request from the LDNS, transmits the CNAME domain name reply to the LDNS and receives the CNAME resolution request from the LDNS.

16. The apparatus according to one of claim 12 , wherein the information about the time based distance between the name server and the LDNS, received by the name server, is information calculated by the name server using at least one of a ping test and trace route.

17. The apparatus according to one of claim 12 , wherein the information about the time based distance between the name server and the LDNS, received by the name server, is information calculated using a time for which the name server generates the CNAME domain name reply indicating that the resolution-requested domain name has been canonically named when receiving the domain name resolution request from the LDNS, transmits the CNAME domain mane reply to the LDNS and receives the CNAME resolution request from the LDNS.

18. The apparatus according to one of claims 11 and 12 , wherein the name server and the probe server are synchronized with each other.

19. The apparatus according to one of claims 10 and 11 , wherein the distance calculation unit of the name server calculates the time based distance between the LDNS and the POP only when the probe server cannot directly calculate the time based distance between the LDNS and the POP.

20. The apparatus according to claim 12 , wherein the distance calculation unit of the probe server calculates the time based distance between the LDNS and the POP only when the probe server cannot directly calculate the time based distance between the LDNS and the POP.

21. The apparatus according to one of claim 20 , wherein the probe server directly calculates the time based distance between the LDNS and the POP using at least one of a ping test and trace route.

22. A non-transitory recording medium storing a program for implementing a method for calculating, by a name server, a distance between a local DNS (LDNS) and a point of presence/POP) in a CDN including a client, the LDNS, the name server, the POP, and a probe server included in the POP, the method comprising: responsive to the name server receiving a domain name resolution request from the LDNS, generating, by the name server, a canonically named (CNAME) domain name reply by adding an identifier to a resolution-requested domain name corresponding to the domain name resolution request; and transmitting, by the name server, the CNAME domain name reply to the probe server, wherein a source IP address corresponding to the CNAME domain name reply transmitted to the probe server is changed to the address of the name server by the probe server and delivered to the LDNS, wherein the name server receives a resolution request for the CNAME domain name reply from the LDNS, wherein the name server calculates a time based distance between the LDNS and the POP by subtracting a time based distance between the name server and the LDNS and a time based distance between the name server and the probe server from a total time from when the CNAME domain name reply is transmitted from the name server to the probe server to when the name server receives the resolution request for the CNAME domain name reply from the LDNS.

23. A non-transitory recording medium storing a program for implementing a method for calculating, by a name server, a distance between a local DNS (LDNS) and a point of presence/POP) in a content delivery network/CDN) including a client, the LDNS, the name server, the POP, and a probe server included in the POP, the method comprising: responsive to the name server receiving a domain name resolution request from the LDNS, generating, by the name server, a CNAME domain name reply by adding an identifier to a resolution-requested domain name corresponding to the domain name resolution request; and transmitting, by the name server, the CNAME domain name reply to the probe server, wherein a source IP address corresponding to the CNAME domain name reply transmitted to the probe server is changed to the address of the name server by the probe server and delivered to the LDNS, wherein the name server receives a resolution request for the CNAME domain name reply from the LDNS, wherein the name server receives information about a time when the CNAME domain name reply is transmitted from the probe server to the LDNS and the name server calculates a time based distance between the LDNS and the POP by subtracting a time based distance between the name server and the LDNS from a total time that is based on the time when the CNAME domain name reply is transmitted from the probe server to the LDNS and a time when the name server receives the resolution request for the CNAME domain name reply from the LDNS.

24. A non-transitory recording medium storing a program for implementing a method for calculating, by a probe server, a distance between a local DNS (LDNS) and a point of presence (POP) in a content delivery network (CDN) including a client, the LDNS, a name server, the POP, and the probe server included in the POP, the method comprising: receiving by the probe server, a CNAME domain name reply from the name server, the CNAME domain reply generated by receiving a domain name resolution request from the LDNS and adding an identifier to a resolution-requested domain name corresponding to the domain name resolution request; changing, by the probe server, a source IP address corresponding to the received CNAME domain name reply to the address of the name server and transmitting the address of the name server to the LDNS; receiving, by the probe server, information about a time when the name server receives a resolution request for the CNAME domain name reply from the LDNS and information about a time based distance between the name server and the LDNS from the name server; and calculating, by the probe server, a time based distance between the LDNS and the POP by subtracting the time based distance between the name server and the LDNS from a total time that is based on the time when the CNAME domain name reply is transmitted to the LDNS and a time when the resolution request for the CNAME domain name reply from the LDNS is received from the name server.